We will examine the natural history of diabetic nephropathy in the first decade after the onset of IDDM by studying patients who have been diabetic for 2-20 years and whose age at onset was 10-40 years. Studies will consist of an examination of kidney size, function, and biopsies at baseline and five years. In the intervening years, GFR will be monitored. Variables including glycemic control, dietary intake, plasma lipids, and BP will be monitored. We hope to determine risk factors/predictors of lesion rate development in IDDM patients.